J. Christopher Dalton

Mechanistic photochemistry of 1-adamantylacetone

Irradiation of I-adamantylacetone (1) results in essentially a quantitative yield of two cyclobutanols, 2 and 3. Quantum yields for the formation of 2 and 3 from the SI and TI states of 1 in benzene and methanol are reported. Formation of cyclobutanols from the excited triplet state of 1 is much more efficient in methanol than in benzene. The cyclobutanol product ratio, 2:3, is 1.0-1.8 for the T I reaction and approximately 5 for the SI reaction. The observed stereoselectivity from the excited singlet state reaction is consistent with the intermediacy of a short-lived 1,4 biradical which undergoes rehybridization, resulting in a preference for rotation and closure to yield 2 rather than 3. The reactivity of the SI and T I states of 1 toward intramolecular y-hydrogen abstraction is determined by fluorescence measurements and Stern-Volmer treatments of 1.3-pentadiene quenching of cyclobutanol formation, respectively. We2 and others3 have recently reported that irradiation of 1 -adamantylacetone (1) results in nearly quantitative formation of two cyclobutanols, 2 and 3 (eq 1). Neither of